This invention relates to an ophthalmic lens system which comprises ophthalmic lenses. The ophthalmic lenses may be adapted for implantation in an eye such as intraocular lenses(IOLS) or adapted to be disposed on or in the cornea such as contact lenses or corneal inlays.
When functioning normally, the natural lens of the eye is somewhat elastic and therefore enables good vision of objects at all distances. This accommodation of the natural lens tends to deteriorate with age such that the ability to see well at all distances is lost and eventually the natural lens becomes basically monofocal.
Likewise, when the natural lens is removed as a result of disease or injury and replaced with an IOL, the natural ability of the eye to accommodate is lost completely. However, an ability to have adequate vision at different distances without using spectacles can be provided by the IOL which is implanted following removal of the natural lens. To this end, the IOL may be multifocal as shown and described, for example, in Portney U.S. Pat. No. 5,225,858, Roffman et al U.S. Pat. No. 5,448,312 or Menezes et al U.S. Pat. No. 5,682,223. Alternatively, the IOL may be of the type which is accommodating in that it can be moved by the eye itself, or monofocal with a depth of focus feature as shown and described in Portney U.S. Pat. No. 5,864,378.
Another approach to overcoming loss of accommodation is to use ophthalmic lenses, such as contact lenses or IOLS, with different optical characteristics for each eye. For example with a system known as monovision one lens has a distance vision correction power and the other lens has a near vision correction power. Another example is shown and described in Roffman et al U.S. Pat. No. 5,485,228. It is also known to implant a distant dominant multifocal IOL in one eye and a near dominant multifocal IOL in the other eye as disclosed in the January 1999 issue of Clinical Sciences by Jacobi et al entitled xe2x80x9cBilateral Implantation of Asymmetrical Diffractive Multifocal Intraocular Lenses,xe2x80x9d pages 17-23.
Ophthalmic multifocal lenses can also be provided with some depth of focus. This is shown and described, for example, in Portney U.S. Pat. No. 5,225,858 and Roffman et al U.S. Pat. No. 5,684,560.
Whether monovision or multifocal ophthalmic lenses are employed, nighttime images may not be the same for both eyes and/or possess halos as when the headlights of an oncoming vehicle are observed. This can significantly reduce the ability of the observer to identify and locate objects near the headlights. For example, halos tend to be created when the patient views a distant object through the near vision portion of the lens, and the greater the add power, the more perceptible is the halo.
For example, this is shown and described in commonly assigned application Ser. No. 09/302,977 filed on Apr. 30, 1999. This application discloses a reduced add power multifocal IOL which reduces the effects of halos. This reduced add power IOL is implanted in a phakic eye in which the natural lens has lost some degree of accommodation, i.e. in partially presbyopic eyes.
Commonly assigned application Ser. No. (Atty. Docket No.: D-2857) filed concurrently herewith also discloses multifocal reduced add power lenses, such as IOLs, which are asymmetric, i.e. have different optical characteristics. However, one of these lenses has an add power for full near vision.
The disclosure of each of the patent applications and patents identified herein is incorporated in its entirety herein by reference.
This invention provides an ophthalmic lens system which improves the ability of the observer to identify and locate objects at near. The invention also significantly reduces nighttime visual phenomena associated with receiving out of focus simultaneous images from multifocal IOLS and obtains other important advantages.
The ophthalmic lens system of this invention may include first and second lenses for use with first and second eyes of a patient, respectively. Each of the first and second lenses has more than one vision correction power and is therefore multifocal. Although this invention is particularly adapted for IOLS, it is also applicable to lenses which can be disposed on or in the cornea such as contact lenses and corneal inlays.
The first lens is biased for distance vision or distance biased. This may be accomplished, for example, by configuring the first lens so that the best visual acuity provided by the lens is for distant objects, for example, objects at infinity. The first lens provides better visual acuity for objects at infinity than the second lens. Preferably, the first lens substantially optimizes visual acuity from distance to intermediate distances. The first lens has a power including a power required for distance vision correction for the patient. The second lens has a power including a power required for intermediate vision correction for the patient. The second lens preferably is intermediate biased. This may be accomplished, for example, by configuring the second lens so that the best visual acuity provided by the second lens is for objects at intermediate distances. Alternatively, or in addition thereto, the second lens provides better visual acuity from intermediate to near distances than the first lens. Preferably, the second lens enhances visual acuity from intermediate to near distances. In addition to the advantages noted above, this enhanced visual acuity of the second lens significantly enhances intermediate vision and provides functional near image quality. It also minimizes potential undesirable effects by using only a low level of image quality disparity between the images received by the two eyes.
The lenses can be made to have the relatively larger ranges of vision in various ways. For example, this can be accomplished by appropriately splitting the light between distance and intermediate. Thus, the second lens may focus sufficient light to an intermediate focus region so as to contribute to the second lens providing enhanced vision from intermediate to near distances.
Alternatively or in addition thereto, the depth of focus of the zone or zones of the lens which provide intermediate vision correction may be appropriately increased to make the second lens have enhanced vision from intermediate to near distances. This may be accomplished, for example, by controlling the aspheric surface design of the lenses. More specifically, the second lens may have a zone with an add power for intermediate vision correction with such zone having optical aberrations which increase the depth of focus of such zone. In one preferred embodiment, such zone extends radially outwardly and has progressively increasing add powers as the zone extends radially outwardly.
The add power of the lenses is reduced over what it would be if one or both of the lenses had the full or even nearly full add power required for near vision correction. The full add power for near vision correction can range from greater than about 1.75 diopters of add power, and is typically between about 2.0 diopters or about 2.5 diopters to about 3.0 or more diopters of add power. The reduced add power significantly reduces halos. Moreover, when the invention is embodied in an IOL which is implanted in a phakic eye with some accommodation, the near visual quality is even better.
In the interest of keeping the add power low while providing adequate vision quality, preferably the maximum add power of either or both of the first and second lenses is less than the add power required for complete or full near vision correction. Still more preferably, the maximum power of any region of either or both of the first and second lenses is no greater than about the power required for intermediate vision correction. By way of example, the maximum add power for both the first and second lenses may be from about 0.5 diopter to about 1.75 diopters and is preferably from about 1 diopter to about 1.5 diopters. The complete near vision correction is typically between 2.5 and 3.0 diopters of add power. All of the add powers set forth herein are in the spectacle plane.
The first and second lenses are adapted to provide some depth of focus. The first lens provides some depth of focus toward intermediate vision correction and preferably the second lens also provides some depth of focus from far vision correction toward intermediate vision correction.
Each of the first and second lenses has an optical axis. Preferably the power of the first lens is different at a plurality of locations radially outwardly of the optical axis of the first lens, and the power of the second lens is different at a plurality of locations radially outwardly of the optical axis of the second lens.
Viewed from a different perspective, the power of each of the first and second lenses changes along a power curve, for example, in a radially outward direction from the associated optical axis. The power curve for the first lens is different from the power curve for the second lens. The power curve of the first lens may at least contribute to the first lens having good visual acuity from distance to intermediate distances and the power curve of the second lens may at least contribute to the second lens having good visual acuity from intermediate to near distances. Each of the first and second lenses may have a power which varies from about the power required for far vision correction to about a power required for intermediate vision correction. In one embodiment, the first lens has a larger range of vision for distance to intermediate distances than the second lens. In the same or a different embodiment, the second lens has a larger range of vision for intermediate to near distances than the first lens.
In one preferred embodiment, the first lens has first, second and third optical zones arranged radially with respect to the optical axis of the first lens with the second zone being intermediate or between the first and third zones and having a greater add power than either of the first and third zones. Similarly, the second lens has first, second and third optical zones arranged radially with respect to the optical axis of the second lens with the second zone being intermediate the first and third zones and having a greater add power than either of the first and third zones of the second lens.
Although the zones can be of various configurations, they are preferably substantially annular and substantially concentric. Preferably, there are at least two zones. Still more preferably, there are three or five of the zones with the innermost and outermost of the zones having a power for far vision correction.
The power in a radial direction can change either gradually or abruptly. The maximum power in each of the second zones may be substantially the same. In one form of the invention, each of the second zones has a power which is substantially constant, and the area, for example, the annular area, of the second zone of the second lens is larger than the area of the second zone of the first lens. This also contributes to the second lens having better visual acuity from intermediate to near than the first lens.
Although IOLS constructed in accordance with this invention may be implanted following removal of the natural lenses, they are particularly adapted for implantation in phakic eyes having some residual accommodation. Even though the lenses of this invention have a reduced add power, the additional optical power provided by the natural lens of the early presbyope allows excellent visual quality from distance through intermediate to near. With the gradual loss of accommodation with age, the image quality at near will decrease but some visual acuity will remain even for the absolute presbyope, i.e. a patient with total loss of accommodation.
According to one aspect of the method of this invention first and second IOLS having different optical characteristics are implanted in the eyes, respectively, of the patient without removing the natural lenses of the patient. Each of the IOLS has a power required for far vision correction and a power required for intermediate vision correction power with the maximum power of each of the first and second IOLS being less than the add power required for near vision correction for the patient.
According to another feature of the method of this invention, first and second ophthalmic lenses are placed on or in the eyes of a patient with the first lens being distance biased and the second lens being intermediate biased. Although the first and second lenses may be contacts or corneal inlays, the features of this invention are particularly adapted for IOLS which can be implanted, respectively, in the eyes of the patient.
The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying illustrative drawings.